Mobile data usage has been increasing at an exponential rate in recent year. A Long-Term Evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simplified network architecture. In LTE systems, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of base stations, such as evolved Node-B's (eNBs) communicating with a plurality of mobile stations referred as user equipment (UEs). However, the continuously rising demand for data traffic requires additional solutions. Interworking between the LTE network and the unlicensed spectrum WLAN provides additional bandwidth to the operators.
The current approaches of interworking of LTE and WLAN suffer from various limitations that hamper the benefits of LTE-WLAN interworking. For example, core network approaches like ANDSF provide rich support for implementing operator policy, providing subscriber specific service, and enabling different kinds of WLAN deployment (e.g., trusted and non-trusted WLANs). However, the core network approaches suffer from significant performance shortcomings. These approaches are unable to react to dynamically varying radio conditions and do not permit aggregation of IP flows over LTE and WLAN access. Some of these limitations have been addressed 3GPP on RAN assisted 3GPP/WLAN interworking (IWK). While the RAN assisted IWK feature promises to improve Quality of Experience (QoE) and network utilization, it is also limited by the inability to aggregate IP flows as well as support of limited traffic granularity at the PDN level.
A potential solution to more fully reap the benefits of LTE-WLAN interworking is to allow LTE-WLAN aggregation (LWA) by integrating the protocol stacks of LTE and WLAN systems. The LTE-WLAN aggregation (LWA) provides data aggregation at the radio access network where an eNB dispatches packets to be served on LTE and Wi-Fi radio link. The advantage is that LWA can provide better control and utilization of resources on both links. LWA can increase the aggregate throughput for all users and improve the total system capacity by better managing the radio resources among users. LWA borrows the concept of existing dual connectivity (DuCo) to let WLAN network being transport to Core Network (CN) for reducing CN load and support “packet level” offload. Under the architecture, eNB can dispatch packets either by LTE or WLAN dynamically to improve UE perceived throughput (UPT). Thus, the dispatcher is responsible to decide how many packets (or the traffic dispatching ratio) are delivered to LTE/WLAN appropriately. The eNB may perform such dispatching based on respective channel condition, loadings, or throughput information, where the different dispatching algorithm may influence UPT a lot.
Under DuCo deployment, with existing CP interface between SeNB, the MeNB is able to identify the shortest and longest packet latency (e.g. cover the backhaul latency, ARQ maximum transmission time, and scheduling latency) to configure the reordering timer value appropriately. Meanwhile, with X2-UP signaling (i.e., DL USER DATA, DL DATA DELIVERY STATUS), the MeNB and SeNB can exchange the successful PDU delivery information and buffer size information to allow the flow control of PDU over the X2 interface. Unfortunately, such CP/UP interface does not exist under LWA and eNB fails to understand the information and WLAN's PDCP PDU delivery status when PDU is delivering to WLAN link. A solution on how to optimize UPT and LWA PDCP PDU dispatching algorithm by means of eNB acquiring channel information, load information, and throughput estimation is sought.